A. Field of the Invention
This invention relates to a novel spin-draw process for producing fully drawn melt spun synthetic filaments, such as, polyester and polyamide filaments, having useful spontaneous crimp and/or latent crimp.
As used herein: the term "spontaneous crimp" means crimp observed upon release at ambient temperatures of the tension applied to the filaments during the drawing thereof; the term "latent crimp" means crimp which is not observed even upon release of the drawing tension until the filaments are subjected to heat while relaxed; the term "crimp" means crimp resulting from the additive effect of both spontaneous and latent crimps; the terms "% hot bulk" and "% cold bulk" are defined by the equation: ##EQU1## where the vertical length (L.sub.2) of a sample of filaments having a length (L.sub.1) (e.g. 25.4 cm) when fully extended (straight) is measured while being maintained in the vertical position by means of a clamp at the upper end of the sample and a weight of 0.0009 grams per denier attached to the lower end. In determining % hot bulk L.sub.2 is determined after the sample has been exposed to 180.degree. C. dry heat for five minutes followed by cooling at ambient conditions for one minute. In determining % cold bulk L.sub.2 is measured without the sample being first exposed to dry heat. Unless otherwise stated herein the term "% bulk" has reference to % hot bulk. Cold bulk is a measure of spontaneous crimp while hot bulk is a measure of both spontaneous and latent crimps.
B. Description of the Prior Art
U.S. Pat. No. 3,832,435 describes a melt spinning process for producing partially drawn polyester filaments having latent crimp. Latent crimp is imparted to the filaments after they leave the spinneret by cooling the freshly spun filaments on one side before they completely solidify. The cooling is accomplished by passing the individual filaments over a cooled roll (quench roll) driven at a given peripheral speed. The yarn is passed from the quench roll over a second cooled roll of smaller diameter which is normally stationary or substantially stationary when compared to the speed of the first roll. The filaments are pulled from the second roll at a speed such that they are partially drawn as they leave the second roll. The partially drawn filaments prepared by this process must be further drawn in a separate operation and then heated to develop the latent crimp.
It is an object of the present invention to provide a simpler, more economical process for producing polyester filaments having a latent crimp.
It is another object of the invention to provide a process for producing in one operation fully drawn polyester filaments having latent crimp.
It is still another object of the invention to provide a process which is also useful for imparting both latent crimp and spontaneous crimp to other melt spun synthetic filaments, such as polyamide filaments.